(1) Field of the Invention
The present invention generally relates to thermal management of semiconductor devices. More particularly, this invention relates to a process and electronic assembly for increasing the dissipation of heat from semiconductor circuit devices, such as power flip chips.
(2) Description of the Related Art
Power flip chips and certain other semiconductor devices require thermal management in order to minimize their operating temperatures. A variety of approaches have been developed for dissipating heat generated by power flip chips. Notable techniques are disclosed in commonly-assigned U.S. Pat. Nos. 6,180,436 and 6,365,964 to Koors et al., which involve conducting heat from a circuit device with a heat-conductive pedestal brought into thermal contact with a surface of the device, e.g., the non-active “topside” surface of a flip chip opposite the solder connections that attach the chip to its substrate. A thermally-conductive lubricant, such as a silicone grease, is placed between the topside of the device and the pedestal to fill gaps between the device and pedestal in order to promote thermal contact, as well as decouple lateral mechanical strains that arise as a result of different thermal expansions and movement between the device, substrate and pedestal. An elastomer or other suitable biasing member urges the device into contact with the pedestal, promoting intimate contact between the device and pedestal to minimize the interface thermal resistance therebetween.
To further reduce induced stresses and to eliminate the need for thermally-conductive lubricants, co-pending U.S. Pat. No. 6,700,195 to Mandel discloses mounting a power flip chip (or other circuit device) within a first region of a substrate. The first region is peripherally supported by a second region of the substrate surrounding the first region, which in turn is supported by a third region of the substrate surrounding the second region. The second region is fabricated to be more flexible than the first and third regions. The device is contacted by a heat-conductive member, and a biasing member contacts the first region of the substrate to bias the device into thermal contact with the heat-conductive member. An important advantage of the assembly disclosed by Mandel is that the more flexible second region of the substrate improves the mechanical decoupling of strains that arise as a result of different thermal expansions and movement between the device, substrate, and heat-conductive member, thereby reducing the induced stresses that can cause fracturing of the device and its solder connections.
While the teachings of Koors et al. and Mandel provide significant improvements for thermally managing circuit devices, further improvements would be desirable, particularly as higher power densities are sought for circuit assemblies.